End-of-train devices (ETDs) are widely used, in lieu of cabooses, for signaling and monitoring purposes in trains that travel on railroads. Information monitored by an ETD may include the air pressure of a brake line, battery condition, as well as train movement. This information may be transmitted to a crew in a locomotive by a battery powered telemetry transmitter. However, existing “dumb” ETDs may only provide a visible indication of the rear of a train with a flashing red taillight. Other rail vehicles sometimes approach from the rear of the train and may get dangerously close to the train. Since an operator of the approaching vehicle is prone to not pay attention (or even fall asleep), the approaching vehicle may run into the end of the train. Therefore, it is desirable to design additional warning mechanisms for preventing collision from the rear.